262 DESCRIPTIVE GEOLOGY. 



istic Jurassic forms, among which the following have been specifically 

 determined: 



Camptonedes hellistriatus. 



Myoplioria lineata. 



Grypliaea calceola. 



Pentacrinus asteriscus. 



Belemnites densus. 

 Within the red Triassic sandstones in the canon are heavy deposits of 

 gypsum, corresponding apparently in horizon to those found in Ashley 

 Creek Basin on the opposite side of the range. The valley of Sheep 

 Creek, from this point eastward, has been worn out of the clayey strata at the 

 base of the Triassic formation, whose beds form almost perpendicular cliffs 

 over a thousand feet in height on its northern side, while its southern wall 

 is formed of the steeply-inclined strata of the Upper Coal-Measure group, 

 through which, at this point, the main branch of this stream, entering it at 

 right angles to ite course, has cut a narrow, picturesque canon. The steep 

 angle of dip here is, however, evidently due to a local compression and 

 lateral flexure of the beds, since it is not maintained to the eastward, and, for 

 a short distance west, strikes of east 30° south were observed. The ridge 

 of Triassic sandstones, which form the northern wall of Sheep Creek and 

 the southern boundary of the Henry's Fork Basin, stretches eastward in the 

 direction of the strike of the beds, viz, east 15° south, to the junction of 

 this stream with Kingfisher Creek. It then bends outward toward the 

 north, in a semicircular or bow-shaped curve, whose other extremity is at 

 Flaming Gorge, the point where the Green River cuts through this ridge ; 

 it presents easy slopes on the north, and a steep bluff face to the south, 

 overlooking a monoclinal valley, which would have seemed to be the 

 natural course of Green River, but which, owing to causes before explained, 

 this river has disregarded, as reference to the map will show, cutting 

 instead a horseshoe-shaped canon in the hard limestones and sandstones of the 

 Upper Coal-Measure group. 



A continuous section of the Jurassic beds was not observed here by us, 

 but the notes given by Professor MarsW show a general correspondence in 



'Amer. Jour, of Sci., Mar., 1871. 



